Thrust III MEMS

1
Thrust III - MEMS

• Red dates denote PI Update Meetings

• Meeting Schedule
• Jan 20
• Feb 3 Matt Aggleton
• Feb 17
• Mar 3 Chris Brown
• Mar 17
• Mar 31
• Apr 21
• Apr 28 Justin Burton
• May 12
• May 26
• Jun 9
• Jun 23
• Jul 7

• Jul 21 Doug Irving
• Aug 4
• Aug 18 Brendan Miller
• Sept 1
• Sept 15 Steve Patton
• Sept 29
• Oct 13 Omid Rezvanian
• Oct 27
• Nov 10 Wes Crill
• Nov 24
• Dec 8 Randy Waldrep
• Dec 22

2
Theory-Brenner-NCSU

• Currently working on
• Domains in SAMs and incorporation at domain
  boundaries
• System size dependence
• Different molecules
• Surface roughness and its effect on transport on
  the SAM
• Step edges and random roughness
• Overview of results/issues
• Early in the surface roughness calculations we
  are seeing transport along the step edges
• Short term goals
• Use first principles to calculate electrostatic
  field for each molecule
• Long term goals
• Finish laundry list of bound mobile combinations
• Monolayer coverage
• Frictional coefficients

Doug Irving
3
Theory-Brenner-NCSU

Different voltages applied through nanowire
with contacts fixed to determine which comes
close to, but less than, melting
0.3V chosen, applied to system, now with right
contact fixed and a constant 80nN applied to left
(sequential snapshots shown below)
Currently working on demonstrating softening
at 100K by pulling above and below this
temperature to get a F vs. T plot.
nanowire dimensions 55Å long, 8Å in diameter
5ps 10ps 15ps 20ps
Wes Crill

4
Modeling-Zikry-NCSU

• Overview of recent results
• - Contact resistance for multi/single-asperity
  contacts / Including hardening, softening and
  temperature effects roughness
• - Asperity Temperature

Contact resistance for an individual asperity
a Asperity contact radius
Overall contact resistance
m Number of asperities in contact
Hardening, softening and temperature effects on
resistivity
needs to be tuned
Asperity temperature
Omid Rezvanian
5
Modeling-Zikry-NCSU

• Overview of recent results

Single Asperity with cylindrical shape
Contact radius 0.5 micron Initial
resistivity 3e-8 ohm.m Ambient temperature
300 k Voltage .1 v Electron
mean free path 50 nm
Omid Rezvanian
6
Modeling-Zikry-NCSU

• Overview of recent results

Multi-Asperity Contact
Initial resistivity 3e-8 ohm.m Ambient
temperature 300 k Voltage .1 v
Omid Rezvanian
7
Modeling-Zikry-NCSU

• Overview of recent results

Multi-Asperity Contact
Initial contact resistance 0.3
Omid Rezvanian
8
Silicon VPL MEMS-Krim-NCSU
Basline WYKO Measurement
Adam Hook
9
Silicon VPL MEMS-Krim-NCSU
WYKO Measurement 21Volt Load
10
Silicon VPL MEMS-Krim-NCSU
Baseline WYKO Measurement 42Volt Levitation
11
Silicon VPL MEMS-Krim-NCSU
WYKO Measurement 42Volt Levitation, 21Volt Load
12
Compensation of Comb Drive Levitation
WYKO Dynamic Height Profile
Waveform Comparison

• Normal operation of shuttle shows widely varying
  height versus phase of waveform, 1 micron
  variation
• Height of contact point around 2.2 microns
• With the shuttle levitation as well as pinch
  actuator levitation the pinch actuators jump
  onto the top of the oscillating shuttle
• Work at Sandia in collaboration with Shannon J.
  Timpe of UC Berkley has resulted in a solution to
  this issue
• Using the equations for levitation and
  electrostatic combdrive actuation we have
  developed a waveform that maintains a constant
  levitation force throughout the x-y plane motion
• Also 2-d electrostatic force density modeling of
  the combfingers has led to a method of combdrive
  design that will almost completely reduce
  levitation to zero in Summit V devices
• And ongoing 3-d simulations will hopefully bring
  to light the exact nature of combdrive levitation
  and lead to further design modifications
• This work has direct impact not only on the MEMS
  portion of the MURI project but also on the
  entire MEMS industry
• Publication of this work is pending (cant think
  of the right word here, basically we are
  conducting experiments in vacuum and waiting on
  ANSIS modeling)

13
RF MEMS Krim NCSU

• Currently working on
• Investigating resistance spike on RF devices
• He vs N environments
• Comparison between operational and fused switches
• Generating samples for AFM testing of surface
  roughness
• Last 6 samples have failed to operate
• Overview of results/issues
• Data points to surface contamination at gold
  contacts as a reasonable explanation for higher
  resistance.
• Short term goals
• One more run on fused switch in He environment
• He vs N2 experiment on operational switch
• Lifetime testing

Chris Brown
14
RF MEMS Krim NCSU

• Currently working on
• Resistance vs Time
• Matching experimental conditions and theoretical
  calculation conditions
• 90 min test run
• 100 micro Amp
• Constant closure, with constant current.
• Papers
• MEMS operation w/ Jim Rutledge
• R vs Time, Zikry
• R vs Temp w/ theory support later in year

Chris Brown